Time : 2 Hours (Model Answer Paper) Max. Marks : 40

Transcription

1 08 00 MT MT - SCIENCE & TECHNOLOGY -I (7) - SEMI PRELIM - I : PAPER - Time : Hours (Model Answer Paper) Max Marks : 40 A (A) Solve the following questions : () The device which converts electrical energy into mechanical energy is called Electric motor () Cassiterite is a tin ore () False - The escape velocity is responsible to launch a rocket in space which can overcome the earth s gravitational force Hence, its velocity should be more than the escape velocity (4) False - It is propanoic acid (5) Hope s Appartus A (B) Choose the correct alternative and rewrite the sentences : () Substance used to decrease the melting point of alumina in Hall - Haroult process Cryolite () If the potential difference across a wire is V and the current through the wire is A, the electric power W () Ice is such a substance which contracts on heating (4) Monomer of polythene is CH CH (5) Geostationary satellite is a High Earth Orbit (HEO) satellite A Solve the following questions : (Any 5) () (i) Nitric acid is a strong oxidizing agent It oxidizes hydrogen (H ) to water (ii) Hence, it oxidizes completely to form any of the nitrogen oxide and water (iii) Hence, these metals do not produce H gas when they react with dilute HNO Eg Cu (s) + 4HNO (aq) Cu(NO ) + NO (g) + H O

2 / MT PAPER () The electric bulb works on the principle of heating effect of electric current (i) The intensity of light emitted by the lament of an electric bulb depends on the temperature of the lament (ii) When electric current is passed through the lament, a large amount of heat is generated and lament becomes hot, then emits light (iii) The melting point of Tungsten is very high (80 C), so that the lament can be heated to a high temperature without melting it (iv) Hence, the lament of an electric bulb is made up of Tungsten () Ethanamine: Molecular formula C NH H H Structural formula : H H C C N H H H (4) The temperature range of 45 C to 55 C is chosen while de ning the unit for heat If we heat kg of water by C in different temperature range than 45 C to 55 C, the amount of heat required will be slightly different (5) Cu (s) + 4HNO (aq) Cu(NO ) (aq) + NO (g) + H O (l) Copper Nitric acid (concentrated) Copper nitrate Nitrogen dioxide Water (6) Ethanol and Ethanoic acid : (i) Ethanol It does not react with NaHCO Ethanoic acid (i) It gives CO with NaHCO (ii) It burns with blue ame (ii) It does not burn with blue ame (iii) (iv) It does not affect blue litmus (iii) It turns blue litmus red The general formula is (iv) The general formula is C n H n- C n H n+ or C n H n (7) Speci c heat capacity : The quantity of heat required to raise the temperature of a unit mass of substance through C is called speci c heat capacity Its unit is J/kgºC

3 A Solve the following questions : (Any 5) / MT PAPER () (i) When the current is downwards, the force experienced by the conductor will be outwards (ii) If the conductor experiences a force inwards, the direction of current would be upwards (iii) Fleming s Left Hand Rule () Given: h 5780 km V 0MM8 km/s M 4 M To nd: T? R 6400 km Formula: V Solution: V GM, V r T GM GM n V Also, r G 4M 4 GM r r V 4 08 (i) GM s [from (i)] ( ) Note: 4 08

4 or hrs hrs The satellite would take hrs 4 / MT PAPER () (a) AB (b) BC (c) Latent heat of vaporisation : The heat energy absorbed at constant temperature during transformation of liquid into gas is called Latent heat of vapourization (4) (a) COOC + NaOH COONa + C OH Saponi cation (b) Substances having ester as the functional group are formed by reaction between a carboxylic acid and an alcohol Ethanoic acid reacts with ethanol in presence of an acid catalyst and ester, ethyl ethanoate is formed -COOH + -CH -OH (Ethanoic Acid) (Ethanol) Acid Catalyst -COO -CH - + H O (Ethyl Ethanoate) (Water) (5) Given: Q A Water/Ice Q B Ammonia (m) kg m (c) kcal/kg C - t 0 C - t 0 C - L 80 kcal/kg 4 kcal/g To nd: m? Formulae: Solution: () Water Water (0 C) Q A Q B Q mc T, Q ml mc T Q A mc T + ml () () Ammonia Q B m L () ml Water (0 C) Ice (0 C)

5 5/ MT PAPER from () and () or Q A Q B mc T + ml m L (0-0) + ( 80) m m 4 00 m 4 00 m 4 m kg m 5865 g Hence, 5865g of ammonia has to be evaporated (6) (a) Air supply Froth Concentrated sulphide ore Bubbles Water and Pine oil Agitator Froth oatation method Gangue (b) Patination of Copper : CO in moist air reacts with surface of copper vessel Copper loses its lustre due to the formation of greenish layer of copper carbonate CuCO on its surface This is called Patination of copper (7) Functional group Hetero atom Name Structural formula Condensed Structural formula Example Halogen (Chlorine, Bromine, Iodine) Halo (chloro, bromo, iodo) X ( Cl, Br, I) X ( Cl, Br, I) Ethyl Chloride or chloro ethane C Cl

6 6 / MT PAPER Oxygen Ketone CO Propanone Alcohol -O-H OH Methanol OH Aldehyde Carboxylic Acid CHO COOH Acetaldehyde CHO Acetic Acid COOH Ether O O Dimethyl ether Ester COO CH -O- Methyl ethanoate COO Methyl amine Nitrogen Amines NH A4 Solve the following questions : (Any ) () (i) In the Hall s process, the ore is powdered and then leached by heating with aqueous sodium carbonate to form water soluble sodium aluminate (ii) Then the insoluble impurities are ltered out (iii) The ltrate is warmed and neutralised by passing carbon dioxide gas through it (iv) This results in the precipitation of aluminium hydroxide 5 (v) Al O H O (s) + Na CO (aq) NaAlO (aq) + CO (g) + H O (l) (vi) NaAlO (aq) + H O (l) + CO (g) Al(OH) + Na CO (vii) The precipitate of Al(OH) obtained in Hall s process is ltered, washed, dried and then calcined by heating at 000 C to obtain alumina (viii) Al(OH) Al O + H O

7 7 / MT PAPER () (a) The device that converts Electrical energy into mechanical energy is called Electric motor (b) Principle of working : Electric motor works on the principle that a current carrying conductor placed in a magnetic eld experiences force (c) Armature coil, Strong magnet, Split ring, Carbon brushes, Battery 5 (d) Working of the electric motor : (i) When the circuit is completed, the current ows in the branch AB of the loop from A to B through the carbon brushes E and F (ii) Since the direction of the magnetic eld is from north pole to south pole, according to the Fleming s left hand rule, a force is exerted on the branch AB in downward direction and CD in upward direction (iii) Thus, the loop and the axle start rotating in an anticlockwise direction (iv) After half rotation, the current in a loop starts owing in the direction DCBA (v) Therefore, a force is exerted on the branch CD in downward direction and on the branch AB in the upward direction, and the loop continues to rotate in the anticlockwise direction (vi) Thus, the current in the loop is reversed after each half rotation and the loop and the axle continue to rotate in the anticlockwise direction